1. Field of the Invention
The present invention relates to a linear motion guide unit that linearly guides an object to be moved, and which is equipped on, for example, a machine tool or industrial robot.
2. Description of the Prior Art
An example of this type of linear motion guide unit of the prior art is the linear motion rolling guide unit shown in FIGS. 1 and 2.
As shown in the drawings, said linear motion rolling guide unit has track rail 201, in which tracks in the form of a pair of track grooves 201a are formed in both the right and left sides along the lengthwise direction, a slider in the form of sliding unit 203 having rolling element circulating path 202 (refer to FIG. 2) and able to move relative to said track rail 201, and a plurality of rolling elements in the form of balls 204, that bear the load between track rail 201 and sliding unit 203 by circulating while rolling over the above-mentioned track grooves 201a accompanying movement of sliding unit 203, and which are arranged and contained within said rolling element circulating path 202.
Sliding unit 203 has casing 206, provided so as to straddle track rail 201, and a pair of end caps 207a and 207b coupled to both the front and back ends of said casing 206. Two seals 208a and 208b are attached with screws 210 to the outer surfaces of each of said end caps 207a and 207b.
In the above-mentioned linear motion guide unit, seals 208a and 208b have the action of wiping off any dust and so forth on track rail 201 at the time of movement of sliding unit 203. Accordingly, sliding unit 203 moves smoothly and damage to balls 204, rolling element circulating path 202 and track grooves 201a caused by entrance of dust is prevented.
However, if the mounting positions of the above-mentioned seals 208a and 208b are incorrect, together with cleaning and sealing effects becoming inadequate, the contact of the lip portions of said seals 208a and 208b with track rail 201 is not uniform, thus inhibiting smooth operation of sliding unit 203. Consequently, considerable effort is required to increase accuracy when attaching seals 208a and 208b, thus being a problem that ought to be solved in terms of improving manufacturing efficiency. In addition, the above-mentioned linear motion guide unit also has the disadvantage of seals 208a and 208b attached with screws 210 being easily shifted out of position as a result of being subjected to impact.
On the other hand, in the above-mentioned linear motion rolling guide unit, lubricant usually in the form of grease is filled between balls 204 and other members demonstrating relative motion for the purpose of obtaining smooth movement and preventing wear of sliding unit 203 as well as suppressing the production of noise accompanying said movement.
Although an adequate amount of this grease is filled during assembly of the linear motion guide unit, it becomes necessary to replenish this grease since it is gradually consumed as the amount of time said linear motion guide unit is used increases. A common means employed to supply this grease involves the attachment of a grease nipple to the sliding unit and injecting grease into said grease nipple with a grease gun.
However, in the case of small linear motion guide units, and specifically with respect to those wherein dimension H is 20 mm or less as shown in FIG. 2, it is difficult to attach a grease nipple due to the limitations on this dimension. Accordingly, with respect to this type of small linear motion guide unit, operation of the machine tool and so forth on which it is equipped must temporarily be stopped, the linear motion guide unit must be removed, and the sliding unit must be disassembled followed by filling with grease. Thus, this results in the disadvantage of causing a delay in work.